The development of a multisensor optronic device requires Size, Weight and Power (SWaP), cost-effective and modular rangefinders while keeping a good range performance. We report on a fully fibered monostatic laser rangerfinder based on a one lens collimator used as the aperture of both the emission and reception channels. This has been possible thanks to the use of a diplexer.
This design makes the system compacter and achieves a 200g system weight. In addition to its low volume, the fully fibered architecture allows designing a building block rangefinder with the collimator sub-system on one side and the laser and electronics cards module on the other side. Both are linked up by only an optical fiber. This kit format enables the rangefinder to better fit in any available space in higher level systems such as gimbals and multi-function imagers. Besides, no alignment is needed, and no parallax error is possible: the alignment between channels is guaranteed by design over the whole range.
The emission/reception channels of the first prototype has a 28mm diameter 80mm focal length lens, and a 1.55μm 100μJ pulsed laser firing in a burst mode. The rangefinder is set in a class 1 configuration, and measures at 1Hz. The achieved Extinction Ratio is 30dB, which is equivalent to a range on NATO targets of 7km. The achieved ER being class 1M at 5Hz is even 32dB, which is equivalent to a range of 8.5km on NATO targets.
More configurations are reported in this article with their associated performance.
Today, it is commonly agreed that mid-range rangefinders (typical range: 10 km) based on fiber laser
technology, constitute the best trade-off between performance and reliability. But to intend to compete with
long-range devices and propose an alternative to bulk solid state laser systems, it is essential to increase
significantly their extinction ratio (ER) compared to the state of the art.
In this paper, we report on successive real-time statistical algorithms performed on 2 different fiber laser
rangefinders and the feasability to achieve an extinction ratio up to 45dB in an eye-safety burst mode. Based
on a bi-static architecture and equipped with a 38 μJ and 125 μJ, 10 ns pulse fiber laser, their intrinsic ER in
single-pulse emission has been measured respectively at 28 and 33 dB. A 45 mm optical aperture receiver
and a specially designed compact electronics complete the device. This alternative to solid-states systems
dedicated to long range application, represents then a cost-effective solution.